AS4 is a secure messaging protocol based on web services. Digital signatures ensure message authorship, and encryption guarantees data security. The sender receives a digital delivery receipt, which serves as proof of timely delivery.
Unlike AS2, AS4 offers both push and pull functionality. This means recipients can actively retrieve messages, as the AS4 server is always accessible. An HTTP connection is established upon communication, and data can be received by connected systems at any time. Data exchange therefore occurs independently of business hours and server availability.